The invention relates to a packaging apparatus for producing blanks by severing them from a sheet of material and for feeding them to a packaging station by means of a blank-conveyor which consists of revolving laterally perforated belts with a conveying side for the blanks which is under a vacuum as a result of suction chambers arranged on the rear face.
For the processing of packaging materials with "critical" properties in packaging technology, special measures are necessary to fix sufficiently the foils or blanks made from them during conveyance. At the same time it is important to guarantee uninterrupted retention both of the continuous sheet of material and of the blanks severed from it, until they are wrapped round the article to be packaged.
A first solution to this problem can be found in German Pat. No. 1,169,361 issued on Apr. 30, 1964. In this proposal the sheet of material is fed to a suction roller, on the outer shell surface of which suction bores open. The blanks are severed from the sheet of material on this suction roller by a revolving severing knife. The individual blanks are then transferred from the suction roller to lateral suction discs on the same axis, which likewise fix the blank laterally by means of suction bores. The article (pack) can be moved through between these suction discs in a radial direction, specifically carrying with it the blank which is pulled off from the suction discs as a result of slipping.
The use of suction discs as a retaining and conveying member for the blanks has proved unfavourable because they are expensive to produce and are tied to specific maximum dimensons. In addition, when the blank (of appropriately large dimensions) loops substantially round the suction discs, it becomes more difficult for the conveyed pack to pull it off from the suction discs.
Consequently, more recent solutions (U.S. Pat. No. 4,151,699 and German Offenlegungsschrift No. 2,949,685 of Dec. 11, 1979) work with laterally perforated belts, the conveying side of which is likewise exposed via suction chambers fixed in place to a vacuum which retains the blank and carries it along. A vertical plane conveying path for the blanks is possible by means of the perforated belts. This path can have sufficient length for separating the necessary conveying and packaging members from one another. Also, it is easier to pull a blank off from the vertical perforated belts by means of a pack conveyed transversely to it.
However, in the known apparatuses with perforated belts of this type, the problem of severing the blanks from the sheet of material, whilst keeping them fixed continuously, has not yet been solved in the best possible way.